In a copending application Ser. No. 489,866, filed May 5, 1983, assigned to the assignee of the present invention, there is disclosed an automatic liquid transfer apparatus for simultaneously filling or diluting, or both, a multiplicity of wells or sample holders, in a microtitre tray for tissue culture and assay of biochemical or chemical reactions. The disclosure of said application is incorporated into this specification by reference thereto. As therein disclosed, a plurality of aligned pipettes, each having a replaceable and disposable tip, are arranged to fill or dilute a multiplicity of wells, generally 24, 48 or 96, organized in an array eight or twelve wells wide. Each well is sized to contain from a few tenths of a milliliter to about ten milliliters. In general such wells may initially be filled by a manifold system including a metering pump and a fill tube associated with but external to each pipette tip. Such filling is quite satisfactory for many purposes, but frequently it is desirable to fill each well, either singly or as a group with a precise amount of liquid. Such precision is desirably within 1% over a range of from about 1 or less to 1000 or more microliters. Further a common manifold or common pump is not suitable for filling or transferring diverse fluids either singly or simultaneously to such a multiplicity of tray wells. For such accuracy the use of the pipettes, including the replaceable tips in accordance with the disclosure in the above-noted application, is essential. A convenient source of a plurality of liquids, such as reagents, analytes, or cell cultures, to be picked up and transferred by such pipettes is also essential for completely automatic operation of the system. Such trays may also be used to collect waste from the microtitre wells or receptacles.